#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
int F(int x)
{
	if (x >= 3)
	{
		return F(x - 1) + F(x - 2);
	}
	else
	{
		return 1;
	}
	
}
int main()
{
	int n = 0;
	scanf("%d", &n);
	int ret = F(n);
	printf("%d\n", F(n));
	return 0;
}